DE 10 2011 088 252 A1 discloses an add-on ratchet for driving screwing fools which serve for unscrewing and tightening screw elements and cast be selectively driven in two rotary directions, with the option that the add-on ratchet can be implemented as a straight add-on part and as an angular add-on part as well provided in a sleeve-shaped housing are two dogs at a distance from one another, which are supported such that they can be rotated relative to the housing but are axially fixed. At their end faces facing each other, the dogs have their peripheral region each provided with a ratchet toothing which have an inverse design with respect to each other. Opposite to the respective ratchet toothing of the two dogs, a drive ring is provided on the side facing the respective dog with a corresponding ratchet soothing that can be coupled to it. The drive ring is mounted in the housing so as to be axially shiftable relative to it and is supported on the respective dog by means of spring means. The add-on ratchet further includes a drive tool which can be rotatably put through a polygonal opening of the dog and can be locked in place with its coupling end in a polygonal profile of the drive ring in a torque-proof manner. By means of the drive took the drive ring or the respective drive ring can be axially shifted away from the dog through which the drive tool can be put, namely to a position where it is uncoupled from it and at the same time to a position where it is coupled to the other dog carrying the screwing tool.
This add-on ratchet is intended for conventional socket wrenches. Two rotatably mounted, axially fixed dogs are comprised which are provided with saw toothings. A non-rotatable, axially shiftable drive ring with a two-sided toothing is employed. Shifting the drive ring allows to change between a left-hand and right-hand rotation.
A further ratchet means is also known from DE 297 25 472 U1. This document discloses a ratchet means for operating a socket, e.g. a hexagonal socket, comprising a drive part with provisions for force introduction, a driven part which is concentrically arranged relative to the drive part and has its outer end face provided with a centrally projecting square trunnion for engaging a square opening of a socket, and a ratchet element or dog element between the drive part and the driven part. A special feature highlighted here consists m that two body parts with substantially identical design of its outer shell surface are provided successively in the rotary axis direction, with at least the drive part having a square insertion opening in its end face axially opposite to the driven pin.
A switchable screwdriver ratchet means is disclosed in DE 199 51 888 A1 in a further development of the last-mentioned prior art. This document discloses a switchable ratchet screwdriver which admittedly comprises counter-rotating freewheels axially arranged in series inside a housing, a central tool shaft and a dog portion at the level of the freewheels, which can be selectively shifted to an active position left/right by means of the freewheels. The highlighted special feature consists in that the screwdriver is constructed in the manner of a ball pen comprising a slim, tubular housing, a shaft protruding from the housing at the front and a switching press button projecting from the rear end and acting against a spring force; in addition, a fastening clip is provided on the housing.
However, in the above document as well as in the above-named utility model two freewheels are used which have internal and opposite toothings. A slide shaft having an external toothing is used in addition. An axial movement of the slide shaft allows to change between a left-hand and right-hand rotation.
However, the existing solutions have several deficiencies that have to be rectified. This means that the solutions imply a high axial space requirement and in most cases have a high radial space requirement, too. A convenient change of the operating mode is not possible. Usually, the add-on ratchet has to be turned. Moreover, the existing solutions cannot be efficiently combined with additional switching means, for instance with a freewheel. Even if a freewheel is applied, this is only possible by pushing out the slide shaft. A reintroduction of the latter is generally jerky, however. Furthermore, the arrangement of the freewheels dictates the order of the traversed switching positions in this case.